With the renewed and ever expanding interest in Stirling engines, efforts have been made to continually improve upon their design. Basic Stirling engine principals of operations are set forth in a text entitled "Stirling Engines" by G. Walker, 1st Edition, 1980. Essentially, in this regard, a Stirling engine operates on the principal of heating and cooling a working fluid (gas), with the expansion and compression of the gas utilized to perform useful work. A variety of designs are illustrated in the aforenoted text with their attendant advantages.
In the Stirling cycle, a working gas is shuttled between two stationary volume chambers or spaces, the expansion space and the compression space. This shuttling is typically performed by a displacer. During operation of the engine, a very small pressure differential exists across the displacer however a large thermal differential exists across the displacer since the temperature of the working gas is different between the expansion (hot) space and the compression (cold) space. To improve the efficiency of the operation of the engine, there is a need to reduce losses resulting from shuttle heat transfer through the displacer which result when the regenerator cooler is bypassed. Since such heat loss is not available to the working fluid, it reduces the engine operating efficiency. However, previous attempts to provide effective thermal resistance in the displacer capable of withstanding the inertia loads associated with displacer motion and practical weight restrictions have not been entirely satisfactory.
Accordingly, there exists a need to compensate for such thermal losses while not unduly complicating nor adding to the weight and the cost of the engine.